High pressure radio frequency/direct current (RF/DC) PVD processes can be used for metal gate, salicide, and contact applications. For example, benefits of using RF/DC PVD can include improved bottom coverage inside a trench or via structure than conventional DC PVD processes. Ring type magnetron or variable-radius ring magnetron (VRAM) designs can be used for RF/DC PVD due to their simplicity of design and ability to provide better bottom coverage than DC magnetrons. However, despite improved bottom coverage, target utilization for DC/RF magnetrons is poor. Thus, even though most of the target material has not been used, the target life is short. Targets including ferromagnetic materials, such as iron (Fe), nickel (Ni), cobalt (Co) and their alloys may have especially short target lives.
Further, RF/DC magnetrons may facilitate process drift over the target lifetime due to uneven wear of the target. For example, as the target erodes, RF energy may be distributed more into a track formed in the target and less into other areas of the target which causes the deposition profile on the wafer to change. For example, if the track is on the target edge, the deposition on the edge of the wafer will increase at a greater rate than other areas of the wafer as the target erodes, resulting in an edge high thickness profile on the wafer.
Further, although some DC magnetrons allow for two or more tracks to form in the target during target erosion from PVD processes, the closed magnetic loop confines the plasma closely near the target and plasma volume inside the chamber is small. As such, metal atoms sputtered from the target have a lower probability of being ionized resulting in reduced bottom coverage.
Therefore, the inventors have provided improved magnetron designs for use in RF/DC PVD processes.